VARIABLE VOLTAGE LOAD TAP CHANGING TRANSFORMER

• US 20090200290A1
• Filed: 10/13/2008
• Published: 08/13/2009
• Est. Priority Date: 10/19/2007
• Status: Abandoned Application

• Current Assignee: David Burns, Paul Gregory Cardinal
• Original Assignee: David Burns, Paul Gregory Cardinal
• Inventors: Cardinal, Paul Gregory, Burns, David
• Application Number:
  US12/250,386
• Publication Number:
  US 20090200290A1
• Time in Patent Office: Days
• US Class Current: 219/488
• CPC Class Codes: E21B 36/04 using electrical heaters
• CPC Class Codes: E21B 43/24 using heat, e.g. steam injection
• CPC Class Codes: E21B 43/30 Specific pattern of wells, e.g. optimising the spacing of wells
• CPC Class Codes: H01F 27/38 Auxiliary core members; Auxiliary coils or windings
• CPC Class Codes: H01F 29/04 having provision for tap-changing without interrupting the load current
• CPC Class Codes: H01J 37/32926 Software, data control or modelling
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: Y10T 29/49083 Heater type

Abstract

Power supply systems for subsurface heaters are described herein. The power supply system includes a variable voltage, load tap changing transformer. Systems and methods for supplying electrical power to subsurface heaters using the variable voltage transformers are also described herein.

Claims

1-1853. -1853. (canceled)

1854. A variable voltage transformer, comprising:

a primary winding configured to be coupled to a voltage power source that provides a first voltage across the primary winding;

a secondary winding electrically isolated from the primary winding, wherein the secondary winding is configured to step down the first voltage to a second voltage that is a preset percentage of the first voltage;

a multistep load tap changer coupled to the secondary winding, wherein the load tap changer divides the second voltage into a selected number of voltage steps, the voltage steps incremented from a selected minimum percentage of the second voltage to a selected maximum percentage of the second voltage; and

wherein an electrical load is configured to be coupled to the multistep load tap changer to provide electrical power to the load with a selected voltage, the multistep load tap changer being configured to tap a selected voltage step in order to provide the selected voltage to the electrical load.

1855. The transformer of claim 1854, wherein the multistep load tap changer is configured to switch the selected voltage step to change the selected voltage provided to the electrical load.

1856. The transformer of claim 1854, wherein the multistep load tap changer is configured to switch the selected voltage step to change the selected voltage provided to the electrical load in response to a change in the electrical load so that the electrical load is provided with relatively constant current.

1857. The transformer of claim 1854, further comprising a control system coupled to the transformer, the control system configured to control the multistep load tap changer so that the multistep load tap changer switches the selected voltage step in response to a change in the electrical load.

1858. The transformer of claim 1854, further comprising a voltage measurement transformer coupled to the secondary winding, wherein the voltage measurement transformer is configured to assess the selected voltage provided to the electrical load.

1859. The transformer of claim 1854, further comprising a switch coupled to the secondary winding, wherein the switch is configured to electrically isolate the electrical load from the transformer.

1860. The transformer of claim 1854, further comprising a control power transformer coupled to the secondary winding, wherein the control power transformer is used to provide power to one or more controllers configured to operate the transformer.

1861. The transformer of claim 1854, further comprising a current transformer coupled to the secondary winding, wherein the current transformer is configured to assess electrical current passing through the secondary winding.

1862. The transformer of claim 1854, wherein the voltage steps comprise equally partitioned voltage steps.

1863. The transformer of claim 1854, wherein the voltage steps comprise non-equally partitioned voltage steps.

1864. The transformer of claim 1854, wherein the electrical load comprises a subsurface heater.

1865. A method for controlling voltage provided to an electrical heater, comprising:

providing electrical power to the heater with a selected voltage using a variable voltage transformer, wherein the variable voltage transformer comprises;

a primary winding configured to be coupled to a voltage power source that provides a first voltage across the primary winding;

a secondary winding electrically isolated from the primary winding, wherein the secondary winding is configured to step down the first voltage to a second voltage that is a preset percentage of the first voltage;

a multistep load tap changer coupled to the secondary winding, wherein the load tap changer divides the second voltage into a selected number of voltage steps, the voltage steps incremented from a selected minimum percentage of the second voltage to a selected maximum percentage of the second voltage, the multistep load tap changer tapping a selected voltage step in order to provide the selected voltage to the heater;

assessing change in electrical resistance of the heater over a selected period of time; and

adjusting the selected voltage provided to the heater by changing the selected voltage step tapped by the multistep load tap changer, wherein the selected voltage is changed in response to the change in the electrical resistance of the heater.

1866. The method of claim 1865, wherein the selected voltage is changed in response to the change in the electrical resistance of the heater such that the electrical current provided to the heater is relatively constant.

1867. The method of claim 1865, wherein the change in electrical resistance of the heater is assessed by using a current transformer coupled to the secondary winding and a voltage transformer coupled to the secondary winding, wherein the electrical resistance is calculated by dividing a voltage assessed from the voltage transformer by a current assessed from the current transformer.

1868. The method of claim 1865, wherein the voltage steps comprise equally partitioned voltage steps.

1869. The method of claim 1865, wherein the voltage steps comprise non-equally partitioned voltage steps.

1870. The method of claim 1865, wherein the electrical heater comprises a subsurface heater.

1871. The method of claim 1865, further comprising assessing an electrical resistance of the heater by using a current transformer coupled to the secondary winding and a voltage transformer coupled to the secondary winding,;

comparing the assessed electrical resistance to a theoretical electrical resistance of the heater; and

changing the selected voltage provided to the heater if there is a substantial difference between the assessed electrical resistance and the theoretical electrical resistance.

1872. The method of claim 1865, further comprising limiting the number of changes in the selected voltage for a set period of time.

1873. The method of claim 1865, further comprising cycling the selected voltage provided to the heater so that the electrical current provided to the heater remains relatively constant.

1874. A variable voltage transformer system for providing power to a three-phase electrical load, comprising:

a first variable voltage transformer coupled to a first leg of the three-phase electrical load;

a second variable voltage transformer coupled to a second leg of the three-phase electrical load;

a third variable voltage transformer coupled to a third leg of the three-phase electrical load;

wherein each of the first, second, and third variable voltage transformers comprise;

a primary winding configured to be coupled to a voltage power source that provides a first voltage across the primary winding;

a secondary winding electrically isolated from the primary winding, wherein the secondary winding is configured to step down the first voltage to a second voltage that is a preset percentage of the first voltage;

a multistep load tap changer coupled to the secondary winding, wherein the load tap changer divides the second voltage into a selected number of voltage steps, the voltage steps incremented from a selected minimum percentage of the second voltage to a selected maximum percentage of the second voltage; and

wherein the corresponding leg of the three-phase electrical load is configured to be coupled to the multistep load tap changer to provide electrical power to the load with a selected voltage, the multistep load tap changer being configured to tap a selected voltage step in order to provide the selected voltage to the corresponding leg.

1875-1894. -1894. (canceled)

1895. A variable voltage subsurface heating system, comprising:

a voltage power source that provides a first voltage;

a subsurface electrical load;

a variable voltage transformer electrically coupled to the electrical load, the transformer comprising;

a primary winding coupled to the voltage power source such that the first voltage is provided across the primary winding;

a secondary winding electrically isolated from the primary winding, wherein the secondary winding is configured to step down the first voltage to a second voltage that is a preset percentage of the first voltage;

a multistep load tap changer coupled to the secondary winding, wherein the load tap changer divides the second voltage into a selected number of voltage steps, the voltage steps incremented from a selected minimum percentage of the second voltage to a selected maximum percentage of the second voltage; and

wherein the electrical load is coupled to the multistep load tap changer to provide electrical power to the load with a selected voltage, the multistep load tap changer being configured to tap a selected voltage step in order to provide the selected voltage to the electrical load.

1896-1917. -1917. (canceled)

1918. A method for controlling voltage provided to an electrical heater, comprising:

providing electrical power to the heater with a selected voltage using a variable voltage transformer, wherein the variable voltage transformer comprises;

a primary winding configured to be coupled to a voltage power source that provides a first voltage across the primary winding;

a secondary winding electrically isolated from the primary winding, wherein the secondary winding is configured to step down the first voltage to a second voltage that is a preset percentage of the first voltage;

a multistep load tap changer coupled to the secondary winding, wherein the load tap changer divides the second voltage into a selected number of voltage steps, the voltage steps incremented from a selected minimum percentage of the second voltage to a selected maximum percentage of the second voltage, the multistep load tap changer tapping a selected voltage step in order to provide the selected voltage to the heater;

assessing an electrical resistance of the heater over a selected period of time and assessing if there is a change in the electrical resistance of the heater over the selected period of time; and

adjusting the selected voltage provided to the heater by changing the selected voltage step tapped by the multistep load tap changer, wherein the selected voltage is changed in response to the change in the electrical resistance of the heater.

1919-1937. -1937. (canceled)

1938. A method for controlling voltage provided to a subsurface electrical heater in a wellbore, comprising:

providing electrical power to the heater with a first selected voltage using a variable voltage transformer, wherein the first selected voltage inhibits arcing in the wellbore, and wherein the variable voltage transformer comprises;

a primary winding configured to be coupled to a voltage power source that provides a first voltage across the primary winding;

a secondary winding electrically isolated from the primary winding, wherein the secondary winding is configured to step down the first voltage to a second voltage that is a preset percentage of the first voltage;

a multistep load tap changer coupled to the secondary winding, wherein the load tap changer divides the second voltage into a selected number of voltage steps, the voltage steps incremented from a selected minimum percentage of the second voltage to a selected maximum percentage of the second voltage, the multistep load tap changer tapping a selected voltage step in order to provide the first selected voltage to the heater;

assessing an electrical resistance of the heater;

providing electrical power at the first selected voltage until the electrical resistance of the heater reaches a selected value;

incrementally increasing the selected voltage provided to the heater to a second selected voltage after the electrical resistance of the heater reaches the selected value;

assessing the electrical resistance of the heater over a selected period of time, and assessing if there is a change in the electrical resistance of the heater at the second selected voltage over the selected period of time; and

adjusting the second selected voltage provided to the heater by changing the selected voltage step tapped by the multistep load tap changer, wherein the second selected voltage is changed in response to the change in the electrical resistance of the heater.

1939-1956. -1956. (canceled)

1957. A method for controlling voltage provided to an electrical heater, comprising:

providing electrical power to the heater with a selected voltage using a variable voltage transformer, wherein the variable voltage transformer comprises;

a primary winding configured to be coupled to a voltage power source that provides a first voltage across the primary winding;

a secondary winding electrically isolated from the primary winding, wherein the secondary winding is configured to step down the first voltage to a second voltage that is a preset percentage of the first voltage;

a multistep load tap changer coupled to the secondary winding, wherein the load tap changer divides the second voltage into a selected number of voltage steps, the voltage steps incremented from a selected minimum percentage of the second voltage to a selected maximum percentage of the second voltage, the multistep load tap changer tapping a selected voltage step in order to provide the first selected voltage to the heater;

assessing an electrical resistance of the heater at the selected voltage; and

cycling the selected voltage provided to the heater by switching the selected voltage step tapped by the multistep load tap changer between at least two voltage steps such that the selected voltage is cycled between at least two voltages after a selected amount of time at each of the at least two voltages.

1958-2481. -2481. (canceled)